Spectrophotometric and spectrofluorimetric determination of indacaterol maleate in pure form and pharmaceutical preparations: application to content uniformity

Two simple, rapid, sensitive and precise spectrophotometric and spectrofluorimetric methods were developed for the determination of indacaterol maleate in bulk powder and capsules. Both methods were based on the direct measurement of the drug in methanol. In the spectrophotometric merthod (Method I) the absorbance was measured at 259 nm. The absorbance‐concentration plot was rectilinear over the range 1.0–10.0 µg mL^?1 with a lower detection limit (LOD) of 0.078 µg mL^?1 and lower quantification limit (LOQ) of 0.238 µg mL^?1. Meanwhile in the spectrofluorimetric method (Method II) the native fluorescence was measured at 358 nm after excitation at 258 nm. The fluorescence‐concentration plot was rectilinear over the range of 1.0–40.0 ng mL^?1 with an LOD of 0.075 ng mL^?1and an LOQ of 0.226 ng mL^?1. The proposed methods were successfully applied to the determination of indacaterol maleate in capsules with average percent recoveries ± RSD% of 99.94 ± 0.96 for Method I and 99.97 ± 0.81 for Method II. In addition, the proposed methods were extended to a content uniformity test according to the United States Pharmacopoeia (USP) guidelines and were accurate, precise for the capsules studied with acceptance value 3.98 for Method I and 2.616 for Method II. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of nucleic acid by [tetra‐(3‐methoxy‐4‐hydroxyphenyl)]–Tb3+ porphyrin as the fluorescence spectral probe in bis(2‐ethylhexyl)sulfosuccinate sodium salt micelle system

A new system for the determination of nucleic acid by rare earth metallic porphyrin of [tetra‐(3‐methoxy‐4‐hydroxyphenyl)]–Tb³⁺ [T(3‐MO‐4HP)–Tb³⁺] porphyrin as fluorescence spectral probe has been developed in this paper. Nucleic acid can enhance the fluorescence intensity of the T(3‐MO‐4HP)–Tb³⁺ porphyrin in the presence of bis(2‐ethylhexyl)sulfosuccinate sodium salt(AOT) micelle. In pH 8.00 Tris–HCl buffer solution, under optimum conditions, the enhanced fluorescence intensity is in proportion to the concentration of nucleic acids in the range of 0.05–3.00 µg mL^?1 for calf thymus DNA (ct DNA) and 0.03–4.80 µg mL^?1 for fish sperm DNA(fs DNA). Their detection limits are 0.03 and 0.01 µg mL^?1, respectively. In addition, the binding interaction mechanism between T(3‐MO‐4HP)–Tb³⁺ porphyrin and ct DNA is also investigated by resonance scattering and fluorescence spectra. The maximum binding number is calculated by molar ratio method. The new system can be used for the determination of nucleic acid in pig liver, yielding satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous chiral separation of tramadol and methadone in tablets,human urine,and plasma by capillary electrophoresis using maltodextrin as the chiral selector

The stereoselective analysis and separation of racemic drugs play an important role in pharmaceutical industry to eliminate the unwanted isomer and find the right therapeutic control for the patient. Present study suggests a maltodextrin‐modified capillary electrophoresis method for a single‐run chiral separation of two closely similar opiate pain relief drugs: tramadol (TRA) and methadone (MET). The best separation method possible for the both enantiomers was achieved on an uncoated fused‐silica capillary at 25°C using 100 mM phosphate buffer (pH 8.0) containing 20% (w v^?1) maltodextrin with dextrose equivalent of 4–7 and an applied voltage of 16 kV. Under optimal conditions, the baseline resolution of TRA and MET enantiomers was obtained in less than 12 minutes. The relative standard deviations (n = 3) of 20 μg mL^?1 TRA and MET were 2.28% and 3.77%, respectively. The detection limits were found to be 2 μg mL^?1 for TRA and 1.5 μg mL^?1 for MET. This method was successfully applied to the measurement of drugs concentration in their tablets, urine, and plasma samples.     

Detection of Xeljanz Enantiomers in Diethyl Amine Active Pharmaceutical Ingredients and Tablets

A high‐performance liquid chromatography (HPLC) method was established to detect Xeljanz enantiomers in active pharmaceutical ingredients (APIs) and tablets. The separation was achieved on a Chiralpak IC column using a mobile phase of hexane‐ethanol‐diethylamine (65:35:0.1, v/v). The detection wavelength was 289 nm. The peak areas and the enantiomer concentrations in the range of 0.15–2.25 μg?mL^?1 were in high linearity, with correlation coefficients higher than 0.999. The recoveries were 86.44% at the concentrations of 7.5, 18.75, and 37.5 μg?mL^?1. The limit of detection (LOD) and limit of quantification (LOQ) were 0.042 and 0.14 μg?mL^?1, respectively. This HPLC method is suitable for detecting the enantiomers of Xeljanz in its APIs and tablets. Chirality 27:235–238, 2015. © 2014 Wiley Periodicals, Inc.     

Investigation of the binding of AuNPs–6‐mercaptopurine and the sensitive detection of 6‐mercaptopurine using resonance Rayleigh light scattering

A highly sensitive method for the detection of 6‐mercaptopurine (MP) by resonance Rayleigh light scattering (RLS) method was developed. Gold nanoparticles (AuNPs) were synthesized by a modified seed method and characterized using transmission electron microscopy (TEM). AuNPs were bound to MP via covalent bonding to form the MP–AuNPs complex, which increased the RLS intensity of MP at 347 nm (increased by 65.7%). Under optimum conditions, the magnitude of the enhanced RLS intensity for MP–AuNPs was proportional to MP concentration in the range 0.0681–1.702 μg mL^?1. The linear regression equation was represented as follows: ΔI _RLS = 9.31 + 82.42c (r  = 0.9948). The limit of detection (LOD, 3σ) was 3.32 ng mL^?1. The system was applied successfully to detect MP in pharmaceuticals. MP recoveries were 99.9–101.7% with a relative standard deviation (RSD) (n  = 5) of 0.59–0.77% for three synthetic samples, and 97.5–110.0% with an RSD of 0.98–2.10% (n =  5) for tablet samples.     

Micelle‐enhanced spectrofluorimetric method for quantification of entacapone in tablets and human plasma

In this paper, a simple and highly sensitive spectrofluorimetric method was developed and validated for the determination of entacapone (ETC). The proposed method is based on forming a highly fluorescent product through the reduction of ETC with Zn/HCl. The produced fluorophore exhibits strong fluorescence at λ_em 345 nm after excitation at λ_ex 240 nm. The use of fluorescence enhancers such as Tween‐80 and carboxy methyl cellulose (CMC) greatly enhanced the fluorescence of the produced fluorophore by 150% and 200%, respectively. Calibration curves showed good linear regression (r2 > 0.9998) within test ranges of 0.05–2.0 and 0.02–1.80 μg mL^?1 with lower detection limits of 1.27 × 10^?2 and 4.8 × 10^?3 μg mL^?1 and lower quantification limits of 4.21 × 10^?2 and 1.61 × 10^?2 μg mL^?1 upon using Tween‐80 and or CMC, respectively. The method was successfully applied to the analysis of ETC in its pharmaceutical formulations (either alone or in presence of other co‐formulated drugs). The results were in good agreement with those obtained using the official method. The methods were further extended to determine the drug in human plasma samples, and to study the pharmacokinetics of ETC. The paper is the first report on the spectrofluorimetric determination of entacapone.     

Resonance light scattering study on the interaction between quinidine sulfate and congo red and its analytical application

The interaction between quinidine sulfate (QDS) and congo red (CR) was studied using resonance light scattering (RLS) technique, ultraviolet–visual spectrophotometry and fluorimetry. In weak acidic medium, QDS reacts with CR to form a supermolecular complex which results in the enhanced RLS intensity. Some important interacting parameters, such as the solution acidity and CR concentration, salt effect and addition order of the reagents, were investigated and optimized. Under the optimum conditions, it was found that the enhanced RLS intensity was in proportion to the concentration of QDS in the range 0.2–8.4 µg mL^?1. The corresponding detection limit was 12.0 ng mL^?1. The results showed that this new method enabled simple, sensitive and rapid determination of QDS and was used for the determination of QDS in urine and simulated huamn serum samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Major changes in forest carbon and nitrogen cycling caused by declining sulphur deposition

Sulphur (S) and nitrogen (N) deposition are important drivers of the terrestrial carbon (C) and N cycling. We analyzed changes in C and N pools in soil and tree biomass at a highly acidified spruce site in the Czech Republic during a 15 year period. Total S deposition decreased from 5 to 1.1 g m^?2 yr^?1 between 1995 and 2009, whereas bulk N deposition did not change. Over the same period, C and N pools in the Oa horizon declined by 116 g C and 4.2 g N m^?2 yr^?1, a total decrease of 47% and 42%, respectively. This loss of C and N probably originated from organic matter (OM) that had accumulated during the period of high acid deposition when litter decomposition was suppressed. The loss of OM from the Oa horizon coincided with a substantial leaching (1.3 g N m^?2 yr^?1 at 90 cm) in the 1990s to almost no leaching (<0.02 g N m^?2 yr^?1) since 2006. Forest floor net N mineralization also decreased. This had consequences for spruce needle N concentration (from 17.1 to 11.4 mg kg^?1 in current needles), an increase in litterfall C/N ratio (from 51 to 63), and a significant increase in the Oi + Oe horizon C/N ratio (from 23.4 to 27.3) between 1994 and 2009/2010. Higher forest growth and lower canopy defoliation was observed in the 2000s compared to the 1990s. Our results demonstrate that reducing S deposition has had a profound impact on forest organic matter cycling, leading to a reversal of historic ecosystem N enrichment, cessation of nitrate leaching, and a major loss of accumulated organic soil C and N stocks. These results have major implications for our understanding of the controls on both N saturation and C sequestration in forests, and other ecosystems, subjected to current or historic S deposition.     

Reproductive biology of Chinese minnow Hemiculterella sauvagei Warpachowski, 1888 in the Chishui River,China

This study describes the reproductive biology of the Chinese minnow Hemiculterella sauvagei. The length‐weight relationship, sex ratio, spawning season, size at first maturity, and fecundity were analyzed based on 685 specimens collected from the Chishui River between July 2011 and July 2012. The relationship between standard length (SL) and body weight (BW) were estimated as BW = 2.14 × 10^?4 × SL^2.801 (R² = 0.839; N = 413; P < 0.05) for females and BW = 1.31 × 10^?4 × SL^3.001 (R² = 0.868; N = 272; P < 0.05) for males. The female to male sex ratio, 1.52 : 1, differed significantly from a 1 : 1 ratio. Females predominated in standard lengths >12 cm. Analyses of the monthly variation in the gonadosomatic index (GSI), the monthly proportions of macroscopic gonadal maturity, and the size distribution of oocytes consistently suggested a prolonged spawning season of H. sauvagei from March to August, with a peak from April to May. Logistic curves describing the relationship between proportion of maturity (P_r) at each length interval and standard length were estimated as P_r = 1/(1 + e^{26.867–0.306SL}) (R² = 0.999; N = 413; P < 0.05) for females and P_r = 1/(1 + e^{10.522–0.142SL}) (R² = 0.999; N = 272; P < 0.05) for males. Size at first maturity was estimated as 7.4 cm for males and 8.8 cm SL for females. Absolute fecundity varied from 563 to 5052, with a mean of 2413 ± 874 oocytes per ovary. The relative fecundity was estimated to be 41–299, with a mean of 171 ± 55 oocytes per ovary. The present study provides useful information for fishery management and resources conservation.     

Utility of Von Pechman synthesis of coumarin reaction for development of spectrofluorimetric method for quantitation of salmeterol xinafoate in pharmaceutical preparations and human plasma

Simple, precise and selective spectrofluorimetric technique was evolved for quantitation of selective β₂ agonist drug namely salmeterol xinafoate (SAL). Utilizing its phenolic nature, a method was described based on the reaction of the studied drug with ethyl acetoacetate (EAA) to yield extremely fluorescent coumarin product which can be detected at 480 nm (λ_ex = 420 nm). The procedure obeys Beer's law with a correlation coefficient of r = 0.9999 in the concentration range between 500 and 5000 ng ml^?1 with and 177 ng ml^?1 for limit of detection (LOD) and limit of quantification (LOQ), respectively. Diverse reaction variables influencing the firmness and formation of the coumarin product were accurately examined and modified to ensure greatest sensitivity of the procedure. The proposed technique was performed and examined according to the US Food and Drug Administration (FDA) guidelines for bio‐analytical methods and was efficiently applied for quantitation of SAL in both pharmaceutical preparations (% recovery = 100.06 ± 1.07) and spiked human plasma (% recovery = 96.64–97.14 ± 1.01–1.52).     

Selective spectrofluorimetric method for determination of Lisinopril in pharmaceutical preparations and in presence of hydrochlorothiazide: Application to content uniformity testing

A novel sensitive and cost‐effective spectrofluorimetric method has been developed and validated for determination of lisinopril (an angiotensin converting enzyme inhibitor) in its pure form and pharmaceutical preparations. The method is based on the reaction of the drug with ninhydrin and phenylacetaldehyde in buffered medium (pH 7.0) to form a highly fluorescent product measured at 460 nm after excitation at 390 nm. Different experimental parameters were optimized and calibration curve was constructed. The fluorescence‐concentration relationship was linear in the range of 0.15–4.0 μg mL^?1. The calculated Limit of detection (LOD) and Limit of quantitation (LOQ) were 0.04 and 0.12 μg mL^?1, respectively. The method was successfully applied for the analysis of pharmaceutical preparations containing the studied drug either alone or co‐formulated with hydrochlorothiazide. The obtained results were in agreement with those of the reported method in respect to accuracy and precession. Moreover, the method was applied content uniformity testing according to United States Pharmacopeia (USP) guidelines.     

Gross nitrous oxide production drives net nitrous oxide fluxes across a salt marsh landscape

Sea level rise will change inundation regimes in salt marshes, altering redox dynamics that control nitrification – a potential source of the potent greenhouse gas, nitrous oxide (N₂O) – and denitrification, a major nitrogen (N) loss pathway in coastal ecosystems and both a source and sink of N₂O. Measurements of net N₂O fluxes alone yield little insight into the different effects of redox conditions on N₂O production and consumption. We used in situ measurements of gross N₂O fluxes across a salt marsh elevation gradient to determine how soil N₂O emissions in coastal ecosystems may respond to future sea level rise. Soil redox declined as marsh elevation decreased, with lower soil nitrate and higher ferrous iron in the low marsh compared to the mid and high marshes (P < 0.001 for both). In addition, soil oxygen concentrations were lower in the low and mid‐marshes relative to the high marsh (P < 0.001). Net N₂O fluxes differed significantly among marsh zones (P = 0.009), averaging 9.8 ± 5.4 μg N m^?2 h^?1, ?2.2 ± 0.9 μg N m^?2 h^?1, and 0.67 ± 0.57 μg N m^?2 h^?1 in the low, mid, and high marshes, respectively. Both net N₂O release and uptake were observed in the low and high marshes, but the mid‐marsh was consistently a net N₂O sink. Gross N₂O production was highest in the low marsh and lowest in the mid‐marsh (P = 0.02), whereas gross N₂O consumption did not differ among marsh zones. Thus, variability in gross N₂O production rates drove the differences in net N₂O flux among marsh zones. Our results suggest that future studies should focus on elucidating controls on the processes producing, rather than consuming, N₂O in salt marshes to improve our predictions of changes in net N₂O fluxes caused by future sea level rise.     

Nonlinear response of stream ecosystem structure to low‐level phosphorus enrichment

相似文献   

Strain variability in fatty acid composition of Chattonella marina (Raphidophyceae) and its relation to differing ichthyotoxicity toward rainbow trout gill cells

Lipid profiles of three strains (Mexico, Australia, Japan) of Chattonella marina (Subrahmanyan) Hara et Chihara were studied under defined growth (phosphate, light, and growth phase) and harvest (intact and ruptured cells) conditions. Triacylglycerol levels were always <2%, sterols <7%, free fatty acids varied between 2 and 33%, and polar lipids were the most abundant lipid class (>51% of total lipids). The major fatty acids in C. marina were palmitic (16:0), eicosapentaenoic (EPA, 20:5ω3), octadecatetraenoic (18:4ω3), myristic (14:0), and palmitoleic (16:1ω7c) acids. Higher levels of EPA were found in ruptured cells (21.4–29.4%) compared to intact cells (8.5–25.3%). In general, Japanese N‐118 C. marina was the highest producer of EPA (14.3–29.4%), and Mexican CMCV‐1 the lowest producer (7.9–27.1%). Algal cultures, free fatty acids from C. marina, and the two aldehydes 2E,4E‐decadienal and 2E,4E‐heptadienal (suspected fatty acid‐derived products) were tested against the rainbow trout fish gill cell line RTgill‐W1. The configuration of fatty acids plays an important role in ichthyotoxicity. Free fatty acid fractions, obtained by base saponification of total lipids from C. marina showed a potent toxicity toward gill cells (median lethal concentration, LC₅₀ (at 1 h) of 0.44 μg · mL^?1 in light conditions, with a complete loss of viability at >3.2 μg · mL^?1). Live cultures of Mexican C. marina were less toxic than Japanese and Australian strains. This difference could be related to differing EPA content, superoxide anion production, and cell fragility. The aldehydes 2E,4E‐decadienal and 2E,4E‐heptadienal also showed high impact on gill cell viability, with LC₅₀ (at 1 h) of 0.34 and 0.36 μg · mL^?1, respectively. Superoxide anion production was highest in Australian strain CMPL01, followed by Japanese N‐118 and Mexican CMCV‐1 strains. Ruptured cells showed higher production of superoxide anion compared to intact cells (e.g., 19 vs. 9.5 pmol · cell^?1 · hr^?1 for CMPL01, respectively). Our results indicate that C. marina is more ichthyotoxic after cell disruption and when switching from dark to light conditions, possibly associated with a higher production of superoxide anion and EPA, which may be quickly oxidized to produce more toxic derivates, such as aldehydes.     

Unequivocal Enantiomeric Identification and Analysis of 10 Chiral Pesticides in Fruit and Vegetables by QuEChERS Method Combined With Liquid Chromatography‐Quadruple/Linear Ion Trap Mass Spectrometry Determination

In this research, 10 chiral pesticides in fruits and vegetables were simultaneously determined using chiral liquid chromatography triple quadrupole‐linear ion trap hybrid mass spectrometry (LC‐QqLIT). The QuEChERS method was applied for sample preparation, and an enhanced product ion (EPI) scan was used to acquire tandem mass spectrometry (MS/MS) spectra for the library search. Parameters including limit of detection (LOD), limit of quantification (LOQ), linearity, relative standard deviation (RSD), and matrix effects were evaluated in five representative matrices (strawberry, leek, cowpea, tomato, and eggplant). Good linearity with coefficient of determination (r²) ≥0.997 was obtained for all 20 enantiomers in these five matrices over the range from 1.0 to 250 µg L^‐1. All the recoveries at 5 and 50 µg kg^‐1 (n = 5) ranged between 70% and 120% with RSD below 20%, indicating satisfactory precision. The LOQ for the enantiomers ranged between 0.05 and 1 µg kg^‐1. Based on the proposed method, 135 commonly consumed fruits and vegetables taken from markets in Guizhou province, China, were analyzed. Enantioselective degradation for the selected chiral pesticides was observed in most of the positive samples. Chirality 27:958–964, 2015. © 2015 Wiley Periodicals, Inc.     

Lake‐type‐specific seasonal patterns of nutrient limitation in German lakes,with target nitrogen and phosphorus concentrations for good ecological status

相似文献   

Determination of Enantiomeric Impurity of Levamlodipine Besylate Bulk Drug by Capillary Electrophoresis Using Carboxymethyl-β-Cyclodextrin

A rapid capillary electrophoresis method using carboxymethyl-β-cyclodextrin (CM-β-CD) as chiral selector was developed and validated for the enantiomeric purity determination of levamlodipine besylate bulk drug. Several parameters for were optimized for a satisfactory enantioresolution, including pH of background electrolyte, the concentration of chiral selector, buffer concentration, capillary temperature and voltage. The highest resolution (Rs = 9.8) was obtained with 4 mM CM-β-CD dissolved in 40 mM phosphate buffer (pH 3.5), at temperature 25 °C and voltage 30 kV, normal polarity. This method was fully validated for the enantiomeric purity determination of the R-amlodipine at the 0.2 % level. The established method was validated in terms of selectivity, LOD and LOQ (0.001 and 0.003 mg mL^?1), linearity (y = 2.8943x + 0.1386, r ² = 0.9991), precision and accuracy (95–104 %). Finally, the method was further applied to investigate the enantiomeric purity of levamlodipine in bulk samples.     

Biological and hydrogeological interactions affect the persistence of 17β-estradiol in an agricultural watershed

17β‐estradiol (E2), one of the natural estrogen compounds, is an endocrine disruptor, and low levels in natural waters can impair the reproductive health of aquatic organisms. Its presence has been reported in animal faecal wastes and some aquatic habitats, including surface waters impacted by intense animal agriculture or sewage contamination. Little is known about its transport in hydrological systems or its persistence in water supplies. We routinely sampled stream and soil water over the growing season in an instrumented 1.2‐km² agricultural watershed in central Virginia. E2 concentrations in stream water ranged from 0.01 to 0.12 ng mL^?1; soil‐water values ranged from 0.03 to 0.18 ng mL^?1. The highest concentrations were observed early in the growing season shortly after application of composted poultry litter to the cropped fields, and values decreased both with hydrological transport distance from the cropped field and over the course of the summer. Given the known application rate, E2 must be lost from the soil solution, and we explored biodegradation as a mechanism for this loss. A bacterial consortium cultured from the poultry compost biodegraded E2 in laboratory flasks amended with solutions of 1 : 1 acetate : glucose at concentrations ranging from 0.1 to 10 g L^?1 dissolved organic carbon (DOC), spiked with 1.8 ng mL^?1 E2, and incubated at different temperatures. A loss of 97–98% of the initial E2 occurred within 180 h in experiments at 22 °C and 28 °C with 1.0 or 0.1 g L^?1 DOC amendments. Higher DOC concentrations and lower temperatures slowed the rates of reaction, suggesting that more readily available carbon inhibits use of the E2 by degrading micro‐organisms. The rapid rates of biodegradation in the laboratory incubations are inconsistent with the persistence of E2 in the watershed. This suggests that either the rates of biodegradation are reduced compared with the laboratory experiments or that E2 probably interacts with the components of the natural environment through complexation, sorption or abiotic transformation in the ageing process that leads to diminished bioavailability.     

Effects of jackbean lectin (ConA) on the feeding behaviour and kinetics of intoxication of the pea aphid, Acyrthosiphon pisum

Mannose‐binding lectins were shown to be useful in creating transgenic plants resistant to insects, including many phloem‐feeding Hemiptera. Before these plants can be used extensively, it is important to understand how these lectins exert their toxic effects on the target organisms. We investigated the feeding alterations induced by presenting the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), with a diet containing the lectin from Canavalia ensiformis (ConA). A series of behavioural experiments were carried out to detect potential sensory mediation of lectin activity. Choice tests performed with a 400 µg ml^?1 ConA diet (3.7 µm of native tetramer) showed that A. pisum quickly rejected the ConA diet, but that this reaction was not typical of a sensory‐mediated phagodeterrent effect. In addition, the aphids did not develop a conditioned taste aversion to the lectin. Diet uptake was evaluated using a radioactive tracer (¹⁴C‐methylated inulin), and showed depression of ingestion only after 16 h at 200 µg ml^?1 or after 8 h at 400 µg ml^?1 ConA. This effect was reversible under our test conditions. No evidence was obtained for early detection of the lectin, even by intoxicated aphids. An electrical penetration graph technique was adapted to artificial diets and provided short‐term continuous analysis on feeding/probing events. At the 400 µg ml^?1 level, adults were affected and had reduced ingestion durations as early as in the first 4 h of contact, but experienced an adaptation to the behavioural alterations induced by lectin feeding. Overall, feeding deterrency following exposure to mannose lectins appeared to be a consequence of intoxication, and not due to a sensory mediated process.     

Effect of inorganic and organic forms of selenium supplementation on development of larval Heliothis virescens

Selenium (Se) is an essential micronutrient for vertebrates though little is known about the effects on insects. Herbivorous insect larvae acquire Se from plant tissues in the inorganic form of sodium selenate and sodium selenite, and in the organic form of selenoamino acids, selenomethionine, and selenocystine. In this study, we document the effects of dietary supplementation with sodium selenite, sodium selenate, selenocystine, selenomethionine, and selenized yeast on the developmental rate of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae). Larvae tolerated high levels of Se (500 µg g^?1 Se) as sodium selenate and to a lesser extent as selenocystine. Lower levels of sodium selenite (>1 µg g^?1 Se) caused increased mortality, reduced rates of pupation, more pupal/adult intermediates, and reduced adult emergence. Selenomethionine proved toxic to larvae at levels above 25 µg g^?1 Se, significantly delaying pupation and raising mortality. Provision of Se as selenized yeast, which contains primarily selenomethionine, was also extremely detrimental to larval development and survival. The results indicate that the impact of dietary Se supplement for insects may differ from vertebrates.